Chemical compositions are added to fuels and lubricants to control the physical and chemical properties of the fuel and lubricant compositions and to improve engine performance. Such additives include dispersants, antioxidants, viscosity index modifiers, corrosion inhibitors, wear reducing agents, extreme pressure agents, and the like. Dispersants are particularly important additives for lubricant and fuel compositions. Dispersants maintain impurities and deposits in a suspended state so that they can be removed from the system by filtration or other means rather than being deposited on internal engine components.
Of the dispersants commonly used in lubricant and fuel applications, polymeric Mannich base additives, hydrocarbyl amine adducts, and hydrocarbyl succinic acid derivatives exhibit desired properties for such applications. Mannich base dispersants are typically produced by reacting alkyl-substituted phenols with aldehydes and amines.
Hydrocarbyl succinic acid based dispersants are derived by alkylating, for example, maleic anhydride, acid, ester or halide with an olefinic hydrocarbon to form an acylating agent as described in U.S. Pat. No. 5,071,919 to DeGonia et al. The acylating agent is then reacted with an amine, typically a polyalkylene amine or polyamine to form a dispersant, such as described in U.S. Pat. Nos. 3,219,666; 3,272,746; 4,234,435; 4,873,009: 4,908,147; and 5,080,815.
Despite the wide variety of additives available for lubricant and fuel applications, there remains a need for improved additives to provide increased deposit control and dispersancy without incurring a cost disadvantage.